Stabilization of unsaturated ketones



portant uses.

Patented June 22, 1948 2,444,006 STABILIZATION OF UNSATURATED KETONES llansllannenberg, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif., acorporation of Delaware No Drawing. Application March13, 1945,

- SerialNo. 582,589 7 a 1': Claims. (01.260-593) aspect of the invention relates to the rendering of these unsaturated ketones color stable under conditions normally encountered during their transportation and/or storage.

Unsaturated ketones find application in many industrial processes. In I their utilization it is generally necessary that they meet exacting speciilcations, one of which is that they be substantially free of coloring matter. These unsaturated ketones, however, are generally prone to undergo deterioration, resulting inthe formation therein of color imparting contaminants. The presence of the color imparting impurities generally renders the unsaturated ketones unsuitable for many of the purposes for which they are intended. Without in any way intending to limit the scope of the present invention by any theories advanced herein to set forth more clearly the nature of the invention, it is believed that the color imparting impurities may well be due to the formation of oxidation products of the unsaturated ketones comprising diketones. It has been found that deterioration and formation of the color imparting impurities is favored by the conditions generally encountered in the storage and transportation of the materials involving their prolonged contact with metal-containing, and particularly ferruginous, materials. A waterwhite unsaturated ketone, such as, for example, mesityl oxide, is often found to become discolored under normal conditions encountered in storage and/or transportation at such a rapid rate that its color is generally of medium yellow to amber after a period of only about fourteen days.

As a result of such contamination of the unsatuated ketones it has generally been necessary to subject the material to a purification operation to render it suitable for many of its more im- Such purification often entails costly operations due to the difiiculty encountered in attempting the separation of the color-impartfing contaminants by generally available means.

The various inhibitors which have heretobefore been proposed to suppress the deterioration of unsaturated ketones, while in some instances fairly effective, are in general unsuited either because of the very short period of their effectiveness, their relative ineffectiveness under conditions generally encountered in storage and shipment, especially when in contact with metalcontaining surfaces, or because of the difliculties encountered in separating the inhibitor, when necessary, after it has-served its purpose- It has now been found that the deterioration of unsaturated ketones particularly with respect to discoloration may be suppressed to at least a substantial degree under conditions generally encountered in shipment and storage, even in the presence of metal-containing surfaces by incorporating therein a relatively small amount of a secondary amine.

The present invention is adapted to the stabilization, particularly with respect to color, of all unsaturated ketones having an unsaturated group of at least three carbon atoms, said unsaturated group having an unsaturated tertiary carbon atom. Examples of this particular group of unsaturated ketones comprise: methyl isopropenyl ketone, ethyl isopropenyl ketone, methyl isobutenyl ketone, propyl isopropenyl ketone, cy-.

clopentyl isopropenyl ketone, allyl isopropenyl ketone, di-isopropenyl ketone, 2-ethyl-butene-1- one-3, 2-propyl-butene-1-one-3, 2-ethy1-pentene- 1-one-3, Z-methyl-pentene-l-one-4, Z-methylhexene-2-one-4, 3-methyl-penetene-2-one-4, 2- methyl-pentene-2-one-4, i3-ethyl-pentene-2-one- 4, 2-ethyl-pentene-2-one-4, isophorone, and the like as well as their homologues, analogues and suitable substitution. products thereof. The invention is, however, particularly applicable to the stabilization, especially with respect to color, of

alpha-beta unsatuated ketones having an unsaturated tertiary carbon atom in the beta position. The following are representative unsaturated ketones of this preferred group towhich the invention is particularly applicable: mesityl oxide, 2-methyl-kexene-2-one-4, 2-methyl-heptene-2-one-4, 2,5-dimethyl-hexene-2-one-4, 2- ethyl-pentene-2-one-4, 3-methyl-hexene-3-one- 5, 3-ethyl-hexene-3-one-5, 2,5-dimethyl-hexadiene-2,5-one.-4 and the like, as well as their homologues, analogues and suitable substitution products thereof.

Although the inhibitors of the invention are applied with particular advantage to the stabilization of the above-defined groups of unsaturated ketones the invention comprises in its broadest scope the stabilization of any normally liquid unsaturated ketone, Examples of such other unsaturated ketones comprised within the scope of the invention are: pentene-1-one-4, hexene-l-onei, hexene-1-one-5, pentene-2-one- 4. 5-methyl-hexene-1-one-4, 5-methyl-hexene-2- one-4, 2,2-dimethyl-hexene-3-one5, 2-methylhexene-3-one-5, hexadiene-1,5-one-4 and the like as well as their homologues, analogues and suitable substitution products.

The stabilizlng materials incorporated in the unsaturated ketones to be stabilized in accordance with the invention comprise, in their broadest scope, the secondary amines. Although these aromatic or mixed aliphatic-aromatic structure.

are peculiarly effective in their 'ability to stabilize the normally liquid unsaturated ketones. Suitable secondary amines, comprise, for example, diethylamine, methylethylamine, n-pro-.

pylmethylamine, n-propylethylamine, di-n-propylamine, isopropylmethylamine, isopropylethylamine, isopropyl-n-propylamine, diisopropylamine, n-butylmethylamine, n-butylethylamine, n-butylisopropylamine, di-n-butylamine, secbutylmethylamine, sec-butylethylamine, sec-butylisopropylamine, sec-butyl-n-butylamine, secbutylisobutylamine, sec butyl-n-tert-butylamine, di-sec-butylamine, isobutylethylamine, isobutyln-propylamine, isobutylisopropylamine, isobutylbutylamine, isobutyl-tert-butylamine, diisobutylamine, tert-butylmethylamine, tert-butyl-n-propylamine, the tert-pentylmethylamines, the tertpentylethylamines, pentylisopropylamine, pentyln-butylamine, pentylisobutylamine, hexylmethylamine, hexyl-n-propylamine, hexylisopropylamine, hexyl-sec-butylamine, hexylisobutylamine, hexylpentylamine, 1,5-dimethylbutylmethylamine, LB-dimethyIbutylethyIamine, 1,3- dimethylbutyl-n*propylamine, 1,3-dimethylbutylisopropylamine, 1,3 dimethylbutylisobutyl amine, 1,B-dimethylbutyl-sec-butylamine, 1,3-dimethylbutyl-tert-butylamine, di(l,3-dimethylbutyl) amine, isopropylheptylamine, isopropylallylamine, isopropylmethallylamine, isopropylcrotylamine, lsopropylstyrylamine, sec-butylmethallylamine, sec-butylcrotylamine, 'l,3-dimethylbutylallylamine, dicyclohexylamine, isopropyl-2-methylcyclohexylamine, the phenyl 4 amber, inthe presence or iron in as short a period as fourteen-days, the incorporation therein or a secondary amine, such as, for example, diisopropylamine, will render it substantially color stable in the presence of iron over periods exceeding three hundred days.

The quantity of the secondary amine added to the unsaturated ketone to be stabilized, may vary within the scope of the'invention. The amount required to attain the desired degree of color stability will vary not only in accordance with the particular unsaturated ketone stabilized but with the particular secondary amine employed. In general, it has been found that the addition of the secondary amine to the unsaturated ketone in an amount ranging from about 0.01% to about 3%, and preferably from about 0.1% to about 1% by weight have been found satisfactory. Higher or lower concentrations of the secondary amine may however be resorted to within the scope of the.invention. The secondary amine may be added to the unsaturated .ketone as such or it may be added to only a portion of the unsaturated ketone and the resulting mixture or alkylamines, tolylisopropylamine, xylyl-sec-butyh amine, naphthylisopropylamine, naphthyl-secbutylamine, mono-methylaniline, piperidine, diphenylamine, phenylethylamine, diethanol amine, morpholine, their homologues, analogues and suitable substitution products.

In contrast to this behavoir of the secondary amines, the primary and tertiary amines are generally not only ineffective as stabilizers but their incorporation into the unsaturated ketones often results in an acceleration of discoloration. Of the secondary amines the secondary aliphatic mono-amines have been found to be outstanding in their ability to stabilize the unsaturated ketones, particularly with respect to color. 01 the secondary aliphatic mono-amines the secondary alkyl mono-amines in which the nitrogen atom is attached to a secondary carbon atom in each of the alkyl groups are particularly preferred. Particularly suitable and preferred amines of this group being di-(sec-but-yl) amine, diisopropylamine, di- (sec-amyl) amines, isopropyl-sec-butylamine, isopropyl-sec-amylamines, sec-butylsec-amylamlnes and alpha-methylbutyl-alphaethylpropylamine.

A particular advantage of the secondaryamines is stabilizers for the unsaturated ketones in ac- :ordance with the invention resides in their effectiveness in the presence of metal-containing ;urfaces. Thus, it has been found that substan- ;ial improvement with respect to color stability )f the unsaturated ketones over prolonged peri- )dS of time, even in the presence of ferruglnous naterials, is obtained by the incorporation theren of the secondary amines. Thus, whereas a iubstantially colorless unsaturated ketone. such 1.5, for example, mesityl oxide, will turn yellow to I per 100 cc.

. was used:

solution then added to the remaining ketone in an amount sumcient to attain the desired concentration of the stabilizer therein.

' The unsaturated ketone may be recovered from the color stable composition of matter, comprising the unsaturated ketone and inhibiting amount or secondar amine, by any suitable means. Thus the secondary amine may generally be readily removed by one or more of such steps compri ing, for example, distillation, fractionation. adsorption, solvent extraction, etc. v

The following examples are illustrative of the invention: EXAMPLE I Twelve samples, each consisting of cc. of mesityl oxide in a glass stoppered, cc. bottle were prepared. To each of ten of the samples there was added an amine in an amount equal to one millimole or the respective amine. To all of the samples containing the added amine, and to one of the samples containing no added amine, there was added a rusty three-inch nail as a source of iron. To further simulate normal storage and transportation conditions all of the samples were stored in the dark at room temperature for 61 days. were carefully examined and their color determined. Color of the sample was obtained and recorded by comparison with standard liquids consisting of aqueous solutions of potassium blchromate which were contained in similar bottles. The following color scale, based upon the color of the aqueous solutions of potassium bichromate C'olpr scale 0. Colorless. 1. Very faint yellow, corresponding to 0.5 mg. KaCrzOv per 100 cc.

2. Faint yellow, corresponding to 1 mg.

3. Very slight yellow, corresponding to 1.5 mg. KgCrzOv per 100 cc.

4. Slight yellow, corresponding to 2.5 mg. KzCrzOv per 100 cc.

5. Medium yellow, corresponding to 5 mg. KzCrzO'z per 100 cc.

6. Dark yellow.

7. Light amber.

8. Dark amber.

'1 These colors were not determined quantitatively.

At freqen-t intervals the samples' KzCraOr The particular amine added to each sample, and the color determination obtained at each examination during the storage period, are indicated in the following Table A:

unsaturated tertiary carbon atom. containing a dialkylamine in an amount suflicient to inhibit discoloration of said unsaturated ketone.

6. An unsaturated ketone stabilized against Table A Storage in days Sample No. Stabilizer added gg 1 3 5 9 12 a1 01 92 Color reading 1 di-isopro ylamine yes 1 l 1.25 1.25 1.5 1.75 2 2.75 3

di(secon arybutyhamine. yes. l 1.25 1.25 1.5 1.75 2 2.5 2.5 morpboline 1 1.25 1.25 1.5 1.75 2 2.15 2.15 di-etiianolamine 1.5 2.5 2.5 2.5 3 3.75 3.76 4.5

EXAMPLE 11 color change comprising a normally liqud unsaturated ketone containing from about 0. 1% o mlsfiree samples each consisting of 100 cc. of about 3% by weight of dnsopmpylamme.

yl oxide in a glass stoppered 125 cc. bottle 7 were prepared To one the samples 3) An unsaturated ketone stabilized against there was added 1 millimole of diisopropylamine. color change comprising a normally l i u To the sample containing the amine, and to one saturated ketone containing from about 0.01% of the two blanks, there was added a rusty three- 90 to about y We t of Iii-(Secondary butyl) inch nail. The three samples were stored in the aminedark for 316 days and the color determined at An unsaturated ketone Stabilized against frequent intervals. The color scale given in Ex- 60101 Change Comprising a normally liquid u ampie I was used. Color readings obtained dururated ketone containing from about 0.01% to ing the storage period are indicated in the followabout by weig t of y a ing Table B: 9. An unsaturated ketone stabilized against Table B Storageindays Sample No. Stabilizer added ggg 1 14 so 78 158 133 249 315 213 Color reading 1.' None no 1.5 5 5 5 5 5 5 2 -do yes 1.5 5 5 1 s s s 3 diisopropylamine yes 1 1 1.5 1.75 1.75 2.75 2.75 2 75 Iclaim as my invention: color change comprising a normally liquid un- 1. Mesityl oxide stabilized against color change r saturated ketone containing from about 0.01% consisting of mesityl oxide containing from about to about 3% by weight of a dialkylamine in which 0.01% to about 3% by weight of diisopropylamine. the nitrogen atom is directly attached to a sec- 2. Mesityl oxide stabilized against color change ondary carbon atom in each of the alkyl groups. consisting of mesityl oxide containing from 0.01% 10. An unsaturated ketone stabilized against to about 3% by weight of a dialkylamine in which color change comprising a normally liquid unthe nitrogen atom is directly attached to a secsaturated ketone containing a secondary amine ondary carbon atom in each of the alkyl groups. of the group consisting of the dialkyl secondary 3. An unsaturated ketone stabilized against amines and the alkyl aryl secondary amines in an color change comprising a normally liquid alphaamount suflicient to inhibit discoloration of said beta unsaturated ketone having an unsaturated unsaturated ketone. tertiary carbon atom in the beta position con- 11. A method of inhibiting the discoloration of taining from about 0.01% to about 3% by weight an alpha-beta unsaturated ketone containing er of a dialkylamine in which the nitrogen atom is unsaturated tertiary carbon atom in the beta podirectly attached to a secondary carbon atom sition which comprises incorporating therewith in each of the alkyl groups. from about 0.01% to about 3% by weight of a 4. An unsaturated ketone stabilized against dialkylamine in whichthe nitrogen atom is atcolor change comprisin a normally liquid alphatached to a secondary carbon atom in each of beta unsaturated ketone having an unsaturated the alkyl groups. tertiary carbon atom in the beta position con- 12. A method of inhibiting the discoloration of taining from about 0.01% to about 3% by weight an alpha-beta unsaturated ketone containing an of a dialkylamine. unsaturated tertiary carbon atom in the beta po- 5. An unsaturated ketone stabilized against sition which comprises incorporating therewith color change comprising a normally liquid unfrom about 0.01% to about 3% by weight of 'a saturated ketone having an unsaturated group of dialkylamine. at least three carbon atoms attached to the car- 13. A method of inhibiting the discoloration of bonyl group, said unsaturated group having an 7 an unsaturated ketone having an unsaturated group 01 at least three carbon atoms directly attached to the carbonyl group, said unsaturated group containing an unsaturated tertiary carbon atom, which comprises incorporating therewith a dialkylamine in an amount sufllcient to inhibit.

discoloration of said unsaturated ketone.

14. A method of inhibiting the discoloration of an unsaturated ketone having an unsaturated group of at least three carbon atoms directly attached to the carbonyl group, said unsaturated group containing an unsaturated tertiary carbonatom, which comprises incorporating therewith from about 0.01% to about 3% by weight or a dialkylamine in which the nitrogen atom is directly attached to a secondary carbon atom in each or the alkyl groups.

15. A method of inhibiting the discoloration a normally liquid unsaturated ketone which comprises incorporating therewith from about 0.01% to about 3% by weight or diisopropylamine. 16. A method of inhibiting the discoloration oil a normally liquid unsaturated ketone which com- 20 Number 8 prises incorporating therewith from about 0.01% to about 3% by weight of a dialkylamine in which the nitrogen atom is directly attached to a secondary carbon atom in each 0! the alkyl groups.

17. A method 01' inhibiting the discoloration of a normally liquid unsaturated ketone which comprises incorporating therewith a secondary amine 01' me group consisting of the dialkyl secondary amines and the alkyl aryl'secondary amines in an amount sumcient to inhibit discoloration of said unsaturated ketone.

HANS DANNENBERG.

I REFERENCES CITED The following references are of record in the file of this patent:

UNITED. STATES PATENTS Name Date Bresler -o June 18, 1940 Dannenberg- .....Aug. 25, 1942 

